Illeana has had show business in her blood since she was a child. The granddaughter of screen legend Melvyn Douglas, Illeana began studying acting at the Neighborhood Playhouse in New York. As a teenager, she acted in many plays and also did standup comedy. In 1988, working for a publicist in New York led to her first movie role. Illeana acted in several Martin Scorsese films. These were small roles, but by learning from actors and directors, Illeana developed her talents.

In 1993, Illeana directed and starred in a comedy short The Perfect Woman (1993) which won Best Short Film at the Aspen Festival. This success was a turning point, and led to larger parts, such as getting a starring role in the commercially successful movie To Die For (1995) with big-name stars. That led to over 20 TV and movie projects. Illeana has developed quite an impressive resumé of work. She provides royal entertainment for her fans (royal being an appropriate word, since it's speculated she was named after Princess Elena).